Features:Pure copper electromagnetic coil with discontinuity and no electromagnetic interference.Strong tapping, stable operation and long service life.Hard metal shell, not easy to deform, the sound reaches 100db, and it is farther and safer.The surface is coated with electroplating technology to make the material more anti-corrosive and less prone to rust and corrosion.Portable wired power supply, easy to install, can be installed on the wall, ceiling and other installation methods.Choose 12V DC / 24V / 220V according to the voltage you use.Specifications:Condition: Brand NewColor: RedMaterial: MetalSize: 4 inches(100mm)Power Mode: ExternalOptional Voltage: 220V/12V DC/24VAlarm Volume: 100dbSurface Treatment: ElectroplatingPackage List:1 * Fire Alarm Bell.